Heat distributor



Dec. 3, 1963 w. l... zlNGERY 3,112,651

HEAT DISTRIBUTOR Filed Nov. 1e, leso 4 FLUID FLOW INVEN TOR. WILBUR L ZINGERY ATTORNEY United States Patent C) 3,135,2,651 HEAT DS'ERRUTGR Wilbur L. Zingery, Lona Beach, tai., assigner to North American Aviation, lne. Fil-ed Nov. le, 1969, Ser. No. 69,773 6 Claims. (Cl. '7d- 5) This invention pertains to means for distributing the heat around an enclosed body, and more particularly around a gyroscopic instrument or the like, to create a predetermined temperature pattern within the heat diS- tributor.

in the precision gyroscope art, the precision of the gyroscope is reduced if mass unbalance occurs. One of the causes of mass unbalance is a difference in temperature across any diameter of the gyroscope.

lf the gyroscope is supported by a dotation fluid, convection or the dotation iluid applies torque to the supported gyroscope which reduces the precision of the gyroscope. Convection is caused by a difference in temperaturc: across any diameter ofthe gyroscope.

lt would seem that one way of reducing the temperature dilerence across a diameter of a gyroscope would be to surround the gyroscope with air, or other iluid, which has a constant temperature. Usually, however, this is not feasible.

Trequently the gyroscope is electrically driven which causes the gyroscope itself to be a heat source. To remove heat from the gyroscope, thereby to prevent the gyroscope from overheating, frequently requires the use of a fluid flow such as an air blast.

lf a flow of iluid is utilized, the fluid dow over an instrument causes an unbalance in the ability of the air to exchange heat. Across a particular diameter of the instrument, for example parallel to the airllow, the air iilm exchanges more heat on the side adjacent the air blast than it does on an opposite end of the diameter away from the air blast. The imbalance in air tlm heat exchange causes a diilerent thermal resistance on each side of the instrument, thereby causing an asymmetric heat flow in the instrument.

To avoid ambiguity in this specilication, the following deiinitions are in order. The thermal resistance of a device is defined as the ratio of the temperature diierence across the device to the heat flow caused by said temperature difference. Diametral temperature difference is defined as the difference in temperature between two points on the same diameter, at equal radius from the cent r, and upon opposite sides of the center.

Asymmetric heat flow in the region of the gyroscopic instrument causes a diametral temperature difference. ln the present state of the art, diametral temperature differences of less than O Gl degrees F. are required. lt is expected that in the future even stricter requirements will prevail.

Without a heat distributor, in accordance with this invention, a diametral temperature dillerence of several degrees is frequently observed.

Applicants first approach to the solution of the problem of a high diametral temperature difference is to lower the thermal resistance of the air iilm by attaching fins to the outer pe iphery of a housing enclosing the floated gyroscope.

lf the diametral temperature difference across the exterior of the housing which encloses the gyroscope is not sufficiently small, this invention contemplates the use of a heat insulating shield having a high thermal resistance relative to the thermal resistance or" the device it er1- closes. The heat insulating shield is symmetrical about the output axis of the gyroscope, the interior thereof forming a surface of revolution about said output axis.

To further decrease the diametral temperature difference, this invention contemplates the utilization of means havin(r low thermal resistance penetrating through the heat insulating shield to the external housing and being positioned along the axis of symmetry of the heat insulating shield. The radius oi the low thermal resistance means is preferably very small, i.e., only large enough to remove the desired quantity of heat, to prevent overheating, frorn the gyroscopic instrument to the external low resistance housing.

An alternative embodiment of the device of this invention utilizes an annular member, havino a thermal resistance which is intermediate the thermal resistance of the gyroscope case, internal to the heat insulating shield, and the thermal resistance of the heat insulating shield, itself. The annular member is symmetrically disposed about the axis of symmetry of the heat insulating shield and extends through the heat insulating shield to conduct heat from the gyroscope to the external housing.

It is therefore an object of this invention to generate a predetermined temperature pattern.

It is another object of this invention to shield a low thermal resistance means relative to an external low thermal resistance means by symmetrically enclosing the first low resistance means with high thermal resistance means, and to channel heat along a predetermined axis of symmetry from the enclosed low thermal resistance means to the external low thermal resistance means,

It is another object of this invention to shield a low resistance means from an external low resistance means by high thermal resistance means, symmetrically disposed about a predetermined axis, and by means having an intermediate thermal resistance, symmetrically disposed about said predetermined axis and positioned in said high resistance means to carry heat to said external low resistance means.

lt is also an object of this invention to reduce mass unbalance of a gyroscopic instrument by reducing the diametral temperature dillerence on the surface of said instrument.

lt is an object of this invention to reduce convection torque applied by the notation fluid to flotation gyroscopes.

lt is a more particular object of this invention to provide a novel heat distributor which is adapted to be utilized in connection with gyroscopic structures, and the like, to create a prede ermined temperature pattern.

These and other objects or the invention will become apparent from the following description taken in connection with the accompanying drawings, in which:

FIG. l is a view partially in section, showing a iirst embodiment of this invention;

FIG. 2 is a View, partially in section, ferred embodiment of this invention; and

FIG. 3 is a view, partially in section, showing a third embodiment of this invention.

La FiG. l, a gyroscopic case 10 is pivoted for at least limited rotation about axis 12. Details of a gyroscopic instrument have been omitted because they are only incidental to the invention. Usually the case 10 of a gyroscopic instrument is fabricated of metallic material which has a low thermal resistance. In any event, regardless of die material of the case of gyroscope lll, the thermal impedance of the case of gyroscope it) is dened as a low thermal impedance.

The region 14 immediately surrounding case 10 is usually filled with a :dotation iluid which is adapted to support most of the weight of case l@ and its contents. Usually the amount of fluid within space 14 is Very small and the clearance between case 1t) and its surrounding structure is also very small so that the thermal resistance of the fluid is insignificant. Axis 12 is usually the output axis of the gyroscope within casing lll.

A high resistance enclosure i6 symmetrically encloses showing a precase l@ to form a surface of revolution about axis 12. l-leat insulating shield 16 could-for examplebe made of Wool, berglass, and the like or it might be a vacuum.

External housing 22 utilizes a plurality of ns 24 which are, preferably, parallel to the direction of applied cooling iluid How, Cooling lluid (which may be liquid or gas) is supplied by a pump (not shown). The use of fins 24 lowers the external resistance of the air lilms surrounding housing 22.

ln FIG. 2, a pair of low thermal resistance means 1S and 23 (usually of metal) penetrate through insulating shield 16 along axis l2 to provide a low resistance path for the flow of heat from gyroscope case lll to external housing 22. Low thermal resistance means 1S and 2t) are symmetrically disposed about the axis 12, and are preferably circularly cylindrical. lt is to be noted that the radial size of low resistance members 1S and 26 may, if desired, be different. ln general, the smaller the radius of the members 1S and 2d, the more uniform is the temperature Within shield 16 to cause the diametral temperature difference to be decreased. Members 18 and 2t) must be only large enough to carry the required amount of heat to prevent overheating. Y

ln FG. 3 is shown a low thermal resistance case of a gyroscope lil mounted for at least limited rotation about` axis 12, a high thermal resistance heat insulating shield 16 enclosing low resistance means 10 and symmetrical about the axis 12. High resistance shield 16 is spaced from case 1G by at least a small space 14, usually illed with iiotation fluid and having a low thermal resistance. Surrounding housing 22 has a low resistance and is adapted to receive heat.

Positioned in heat insulating shield 16 is a pair of axially spaced-apart annular members 26 and 2S, symmetrically disposed at a predetermined inner radius about axis 12, each having a thermal resistance intermediate the resistance of heat shield 16 and the resistance gyroscope case 10. Members 26 and 28 are preferably positioned at extreme ends of heat insulating shield 16 to cause the heat llow to have primarily an axial component within the region of case 10. The flow of heat in a radial direction becomes appreciable only in the region of members 26 and 28. By making the thermal resistance of members 26 and 2S appreciably high relative to the thermal resistance of case 10, diametral temperature difference on the exterior side of members 26 and 2S cause only insignicant diametral temperature differences on the interiors thereof to cause heat to ow symmetrically outward around the inner periphery of members 26 and 28. By making the thermal resistance of members 26 and 2S relatively low compared to the thermal resistance of member 16, the majority of heat is channeled axially toward members 26 and 28, and only a negligible amount of heat ows through the walls of members 16. The area of members 26 and 23 internal of members 16 are preferably as small as possible to remove only the required amount of heat to prevent deterioration of the gyroscopic instrument within case lil.

lf-for example-case 1li is metallic, external housing 22 is metallic, and heat insulating shield 16 is glass Wool, an example of material which would be suitable for members 26 and 28 is a ceramic or metal ceramic combination.

ln a preferred embodiment of this invention, the thermal resistance of member 26 and 2li preferably is at least l() times the thermal resistance of member lil and the thermal resistance of heat insulating shield 16 preferably Vis at least l times the resistance of members 26 and 28.

it is preferable to use fins to reduce the diametral temperature difference on the exterior of housing 22. lt is apparent that if the diametral temperature difference is reduced on the exterior of housing 22 that it is also reduced on the interior of heat shield 16 in the region of otation fluid 14.

In operation, fins 24 of housing 22 reduce the thermal resistance of the fluid or air film adjacent housing 22 to cause the impedance ofthe air hlm to be insignificant compared to the resistance of the high resistance member 16.

Because the thermal resistance of opposing sides of case 19 are substantially the same, and because the resistance of the air iilm on either side of housing 22 is small compared to the impedance of member 16, substantially equal qualtities of heat flow in opposing diametral directions from case it) thereby decreasing the diametral temperature difference in region 14.

ln FIG. 2, by making the thermal resistance of low resistance means 18 and 2G very small compared to the thermal resistance of heat insulating barrier 16, substan- Y tially all of the heat is caused to flow through means 1S and Ztl into housing 22. By making low resistance means 18 and 2t? as small as possible, the heat in the region of fluid J- is caused to travel substantially axially to cause a balance flow of heat so that the diametral temperature difference approaches zero.

n HG. 3, because the thermal resistance of heat barrier 16 is very high relative to the thermal resistance of annular members 26 and 28, heat is caused to dow axially until it reaches the region of members 26 and 28. Because the thermal resistance across a diameter of gyroscope case 1t) is very low compared to the thermal resistance of annular member 26 the resistance of member 26 controls the oW of heat to cause it to be substantially uniform in the region of flotation fluid 14, thereby decreasing the diametral temperature dilference. Further, a similar situation prevails in annular member 2S.

Thus, the device of this invention is a heat distributor that is adapted to reduce substantially to zero the diametral temperature difference in the region of the otation iluid of a gyroscopic instrument While allowing the internal temperature to be maintained below some maximum value.

Although the invention has been described and illustrated in detail, it is to be understood that the same is by Way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. In combination: symmetrical gyroscopic means, said gyroscopic means having a case that has a low thermal resistance and Which is symmetrical about a predetermined output axis of said gyroscopic means; a heat insulating shield having a high thermal resistance, enclosing said low thermal resistance case, and symmetrically disposed about said axis to form an internal surface which is a surface of revolution about said axis; external housing having low thermal resistance surrounding said heat insulating shield; means having an intermediate thermal resistance which is substantially less than the thermal resistance `of said insulating shield and substantially more than the thermal resistance of said gyroscopic case and having an annular shaped inner surface; said intermediate l resistance means having an internal annular surface, positioned symmetrically relative to said output axis, and said intermediate resistance means penetrating through said insula-ting shield to carry heat to said external housing means.

2. A device as recited in claim 1 and further comprising tins on the periphery of said external housing means and fluid flow means contacting said enclosing housing and said fins to remove heat therefrom in a symmetrical pattern.

3. In combination: a symmetrical heat source, including means having a loW thermal resistance; a heat insulating shield, having a thermal resistance which is at least 10 times as great as said low thermal resistance, symmetrically disposed relative to a predetermined axis and at least partially enclosing said heat source; a second low thermal resistance enclosing structure enclosing said insulating shield, having tins about its periphery immersed in a moving fluid; and a lthird low thermal resistance means, penetrating through said insulating shield along the axis or symmetry of said shield to conduct heat from said heat source to said enclosing structure.

4. A device as recited in claim 3 wherein said last named low thermal resistance means is symmetrical about said axis of symmetry.

5. A device as recited in claim 3 in which said heat insulating shield completely encloses said heat source and has heat removing tins on its outer periphery.

6. In combination: a irst symmetrical low thermal resistance member; a symmetrical high thermal resistance heat insulating shield, symmetrically enclosing said low resistance member; a second low thermal resistance member symmetrically disposed about said insulating shield;

and a third 10W thermal resistance means positioned on the axis of symmetry of said heat insulating shield and penetrating therethrough to Contact said second low thermal resistance member.

References Cited in the file of this patent UNITED STATES PATENTS 2,711,882 Narbutovskih June 28, 1955 2,768,046 Evans Oct. 23, 1956 2,960,873 Lundberg Nov. 22, 1960 3,044,309 Buchhold July 17, 1962 FORETGN PATENTS 182,506 Great Britain July 3, 1922 

6. IN COMBINATION: A FIRST SYMMETRICAL LOW THERMAL RESISTANCE MEMBER; A SYMMETRICAL HIGH THERMAL RESISTANCE HEAT INSULATING SHIELD, SYMMETRICALLY ENCLOSING SAID LOW RESISTANCE MEMBER; A SECOND LOW THERMAL RESISTANCE MEMBER SYMMETRICALLY DISPOSED ABOUT SAID INSULATING SHIELD; AND A THIRD LOW THERMAL RESISTANCE MEANS POSITIONED ON THE AXIS OF SYMMETRY OF SAID HEAT INSULATING SHIELD AND PENETRATING THERETHROUGH TO CONTACT SAID SECOND LOW THERMAL RESISTANCE MEMBER. 